Hello!
1. I sample something with sample rate of 44100Hz and then save file as .raw.
2. I load the same file but now when the wave editor ask for sample rate I change it to 96000 Hz and I change my soundcards sample rate also to 96000 Hz.
3. Now I have same sample but it's pitch is shifted higher than octave without aliasing artefacts.
Is this true? This works backwards too for example 96000 --> 44100 or 88200 --> 44100 (octave)...
Or is there aliasing artefacts?
Sample Rate Trick?
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- KVRAF
- 6937 posts since 4 Jun, 2004 from Utrecht, Holland
Although I don't see directly what you want to achieve or gain with this procedure: yes, true. There won't be any extra aliasing introduced with this procedure since the samples themselves are not affected with your procedure.
But: any aliasing that already was present will ofcourse not go away. Some cheap onboard soundcards (like AC97 but also SB128PCI) have the hardware sampling frequency fixed to 48kHz. The driver simply skips about each 12th sample to convert the frequency, which introduces alias-like artefacts (frequencies that were not there.) In that case you're better off sampling at 48kHz. Then also it will be shifted up exactly one octave when you convert to 96kHz.
I recommend you to do a test by sampling a slow sine sweep that goes all up to 24kHz and view the spectrum for aliasing evidence. As a by-product you will see the true frequency response of your soundcard.
But: any aliasing that already was present will ofcourse not go away. Some cheap onboard soundcards (like AC97 but also SB128PCI) have the hardware sampling frequency fixed to 48kHz. The driver simply skips about each 12th sample to convert the frequency, which introduces alias-like artefacts (frequencies that were not there.) In that case you're better off sampling at 48kHz. Then also it will be shifted up exactly one octave when you convert to 96kHz.
I recommend you to do a test by sampling a slow sine sweep that goes all up to 24kHz and view the spectrum for aliasing evidence. As a by-product you will see the true frequency response of your soundcard.
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- KVRer
- Topic Starter
- 16 posts since 14 Jul, 2003
Thanks for your reply! I have Creamware Luna II. I think it has one of the better converters in the normal price range.
One trick I will try with this technique.
1. I sample something with sample rate of 44100.
2. Change sample rate and soundcard sample rate to 96000 Hz.
3. Now I feed my guitar amp spring reverb with this signal and sample the resulting reverberated signal back to computer. (still 96000 Hz)
4. Now I change this reverberated signal to 44100 Hz.
Now I shoud have 44100 Hz normal pitch sample with larger sounding spring reverb. Maybe it will sound little like plate reverb. I will try the same thing with small room and mic. --> bigger room sound!
One trick I will try with this technique.
1. I sample something with sample rate of 44100.
2. Change sample rate and soundcard sample rate to 96000 Hz.
3. Now I feed my guitar amp spring reverb with this signal and sample the resulting reverberated signal back to computer. (still 96000 Hz)
4. Now I change this reverberated signal to 44100 Hz.
Now I shoud have 44100 Hz normal pitch sample with larger sounding spring reverb. Maybe it will sound little like plate reverb. I will try the same thing with small room and mic. --> bigger room sound!
